The present invention relates to methods of recovering valuable components present in waste streams and effluents from anaerobic digestion systems, and more particularly comprises a partitioning method for recovering salts of volatile fatty acids, as well as undenatured enzymes in valuable forms.
The coexistence of small organic species, like acids and alcohols, with protein molecules is a common occurrence in various processing streams. For example, fermentation broths usually contain acids, vitamins and enzymes and are formed in conjunction with the manufacture of some industrially important proteins or in the cultivation of bacteria or fungi as extracellular components. Similar materials are found in the sera of animals and humans and as effluents in waste streams from meat processing streams, as well as in anaerobic digester effluents, (eg. from cattle rumens for instance), and all said examples present industry with a continuing disposal problem.
Further, it is known that said waste streams and anaerobic digester effluents typically contain components including valeric, acetic, propionic and butryic volatile fatty acids, and enzymes such as alpha-amylase and cellulase, as well as other proteins, many of which components are valuable and can be sold if available in separated-out, usable, form. And, as an added benefit, where such components are separated-out of waste streams or anaerobic digestion system effluents, the remaining waste or effluent can be easier to process to the point it can be disposed of, as the BOD requirement is often reduced.
As well, regarding waste streams or effluents such as are developed in meat processing plants, the recovery of useful chemicals therefrom, or their complete treatment is often mandated by local or federal regulations, (eg. where acetic and other carboxylic acids are present in the waste materials).
Beneficially, separation of valuable acids and/or enzymes can convert a waste stream into a value added stream and thereby create positive cash flow where otherwise disposal costs are required.
With the foregoing in mind, it is noted that adsorption combined with extraction, has long been the method of choice when other conventional separation methods prove too expensive and/or are energy intensive.
As described by Eyal and Canari in an article titled xe2x80x9cPh Dependence of Carboxylic and Mineral Acid Extraction by Amine-based Extractants: Effects of pKa, Amine Basicity, and Diluent Propertiesxe2x80x9d, Ind. Engng. Chem. Res. 34:5 1789-1798 (1995); and by Ganguly and Goswami in an article titled xe2x80x9cSurface Diffusion Kenetics in the Adsorbtion of Acetic Acid on Activated Carbonxe2x80x9d, Sep. Sci. Tech. 31:9 1267-1278, (1996); adsorption and extraction are commonly used methods for the separation of acids from dilute streams.
Low molecular weight aliphatic carboxylic acids appear in many industrial and effluent streams and the recovery thereof by solvent extraction, with or without reaction, has been studied by Shama and Jagirdar and reported in an articel titled xe2x80x9cRecovery and Separation of Mixtures of Organic Acids from Dilute Aqueous Solutionsxe2x80x9d, J. Sep. Proc. Technol., 1:2 40-43, (1980).
Amine-based extractants, because of their effectiveness and selectivity, are favored over other extractants in the recovery of acids from aqueous solutions as reported in an article titled xe2x80x9cExtraction of Carboxylic Acids With Tertiary and Quaternary Amines: Effect of pHxe2x80x9d, Yang et al., Ind. Engng. Chem. Res. 10:6 1335-1362, (1991).
Partitioning studies of various organic compounds using both adsorbents and extractants have also been documented by King in an article titled xe2x80x9cAcid-base Equilibriaxe2x80x9d in the encyclopedia of Physical Chemistry and Chemical Physics, Pergamon Press, Oxford (1965); and in an article titled xe2x80x9cCoupling Ion Pair Extraction With Adsorbtion for the Separation of Acidic Solutions for Waterxe2x80x9d, Payne and Ramarkrishnan, Ind. Eng. Chem. Res., (1995).
Adsorbents are generally employed in separations using column liquid chromatography for proteins and other organic solutes. Adsorption of molecules of different sizes and surface charges has been investigated by Tien in an article titled xe2x80x9cAdsorbtion Calculations and Modelingxe2x80x9d, Butterworth-Heinemann, Mass. (1994).
Recently amine-based experiments to extract and recover alpha-amylase from reverse micellar solutions has been reported by Chang and Chen titled xe2x80x9cPurification of Industrial Alpha-amylase by Reversed Micellar Extractionxe2x80x9d, Biotech, Bioengng, 48, 745-748, (1995).
It is noted that a use for salts of (APB""s) is as de-icers as discussed in an article titled xe2x80x9cChemical Deicers and the Environmentxe2x80x9d, D""Itrl, Lewis Publishers, Mich., (1992).
Further, commonly utilized de-icers are more corrosive than are esters, such as an acetate, as reported by Reisinger and King in an article titled xe2x80x9cExtraction and Sorbtion of Acetic Acid at pH Above pKa to form Calcium Magnesium Acetatexe2x80x9d, Ind. Sep. Proc. Technol., 34, 845-352, (1995), hence use of metal esters such as CaMg Acetate, CaMg Propionate etc. can be projected as providing environmentally friendly results.
It is specifically noted that for any dilute aqueous stream which contains acids and enzymes, the operating parameters for separating out the acids are different than those for recovering the enzymes and importantly, successful simultaneous separation of both acids and proteins has not before been reported. The present invention, however, teaches that uptake of carboxylic acids and enzymes, alpha-amylase and cellulase from solution can be achieved, where the enzymes are preferentially sequestered, either by leaving the acids in solution or by partitioning the acids into a different phase. And, since unlike solutes do not compete simultaneously with the non-aqueous phase (organic or solid), high percentage separations for acids and enzymes can be achieved.
Present invention experimental work has focused on acetic, propionic and butyric acids and protein compounds including alpha-amylase arid cellulase, (which enzymes are industrially important in degradation of starch and cellulose, respectively), but the approach of using an organic extractant and solid adsorbent to simultaneously separate acids and enzymes is applicable to other systems.
The principal advantage of using organic extractant and solid adsorbent to simultaneously separate acids and enzymes is the ease with which these phases can be separated from an aqueous phase. The extractant and solid phases can be separated from the aqueous phase and the respective phases can be stripped of solutes, allowing the process to be made continuous.
If one solute shows a distinct affinity towards an adsorbent/extractant in the presence of other solutes, then it can be recovered initially.
A Search of Patents has provided a Patent to Monick et al., U.S. Pat. No. 4,765,908 which describes a process and composition for removing contaminants from wastewater. Many chemical compositions are identified for removing heavy metals such as Sodium and Calcium Bentonite, Montmorillonite, calcium carbonate, calcium oxide, calcium hydroxide, lime, aluminum sulfate and a catalist, zirconium. Recovery of enzymes is not a focus.
U.S. Pat. No. 4,675,114 to Zagyvai et al., describes a process for dewatering sludges containing proteinic organic contaminates and for separating solid particles from the aqueous phases. The use of calcium hydroxide and/or magnesium oxide to produce an alkaline sludge pH is mentioned. The use of formaldehyde is described and the methodology does not focus on sequential removal of enzymes followed by removal of other elements.
U.S. Pat. No. 4,629,785 to McCaffery, III, describes a procedure in which proteinaceous material is separated from cationic species by an adsorption process. Converting active microorganisms to inactive form is disclosed.
U.S. Pat. No. 2,171,198 to Urbain et al., describes use of Zinc Oxide to remove and recover fatty acids from waste.
U.S. Pat. No., 3,738,933 to Hollo et al., describes a process for recovering protein from sewage which uses bentonite or kaolin in combination with a calcium compound such as lime milk or calcium hydroxide, aluminum, bi and tri-valent iron.
U.S. Pat. No. 445,055 to Giebermann describes the use of alumina to sequester gluten in slaughter house washings.
U.S. Pat. No. 2,261,923 to Pittman describes use of bentonite to sequester protein from distillery slop.
No known prior teachings, however, provide for partitioning of acids and enzymes into different phases to allow separate undenaturing processing thereof, while leaving unpartitioned solutes in an aqueous phase.
A need is thus identified for economical, easy to practice, methods for separating-out volatile fatty acids, enzyme and possibly other protein components from waste streams and anaerobic digester effluents, and providing said separated-out components are in forms which have economical value.
The present invention provides at least three specifically identifiable modifications of a procedure, the practice of which results in separation of, at least, volatile fatty acids in a valuable salt form which can be, for instance, used as a de-icer. In addition, the present invention procedure can also provide enzymes, (eg. in particular alpha-amylase and cellulose), in undenatured, separated-out form.
The First variation of the present invention can be recited as a method of providing xe2x80x9cpaunchatexe2x80x9d comprising salts of volatile fatty acids comprising, in any functional order, the steps of:
a. providing a waste stream or anaerobic digester system effluent which comprises volatile fatty acids typically including acetic and/or propionic and/or butyric acids, as well as proteins and/or enzymes typically including alpha-amylase and/or cellulase;
b. optionally separating-out particulate solids therefrom;
c. mixing oxides comprised of at least one selection from the group consisting of: (any Group IIA and Group IIB Metal Oxide), into the solution resulting from practicing step a. and optionally step b., such that xe2x80x9cpaunchatexe2x80x9d comprising volatile fatty acid salts is provided in a separated-out form.
The Second variation of the present invention can be recited as a method of separately providing:
enzyme(s) typically including alpha-amylase; and
xe2x80x9cpaunchatexe2x80x9d comprising salts of volatile fatty acids;
comprising, in any functional order, the steps of:
a. providing a waste stream or anaerobic digester system effluent which comprises a solution of volatile fatty acids including acetic and/or propionic and/or butyric acids, as well as proteins and/or enzymes tyically including alpha-amylase and/or cellulose;
b. optionally separating-out particulate solids therefrom;
c. subjecting the solution resulting from practicing step a. and optionally step b. to enzyme adsorption, and optionally desorption, such that at least alpha-amylase is provided in undenatured separated-out of solution form;
followed by:
d. mixing oxides comprised of at least one selection from the group consisting of: (any Group IIA and Group II Metal Oxide), into the remaining solution resulting from practice of step c., such that xe2x80x9cpaunchatexe2x80x9d comprising volatile fatty acid salts is provided in a separated-out form.
The Third variation of the present invention can be recited as a method of separately providing:
enzymes, typically including alpha-amylase; and
xe2x80x9cpaunchatexe2x80x9d, typically comprising salts of volatile fatty acids;
comprising, in any functional order, the steps of:
a. providing a waste stream or anaerobic digester system effluent which typically comprises a solution of volatile fatty acids including, typically, acetic and/or propionic and/or butyric acids, as well as, typically, proteins and/or enzymes typically including alpha-amylase and cellulase;
b. optionally separating-out particulate solids therefrom;
c. treating the solution resulting from practicing step a. and optionally step b. to organic enzyme extractant in the presence of a selection from the group consisting of: (bentonite and functional equivalents thereto), such that adsorption of at least alpha-amylase onto said selection from the group consisting of: (bentonite and functional equivalents thereto) occurs, optionally followed by causing desorption of said alpha-amylase from said selection from the group consisting of: (bentonite and functional equivalents thereto), such that at least said alpha-amylase is provided in an undenatured separated-out of solution form;
said method further comprising:
d. mixing oxides comprised of at least one selection from the group consisting of: (any Group IIA and Group IIB Metal Oxide), into the remaining solution resulting from practice of step c., such that xe2x80x9cpaunchatexe2x80x9d comprising volatile fatty acid salts is provided in a separated-out form, accompanied by recovery of said organic enzyme extractant.
In any of the foregoing examples, the xe2x80x9cpaunchatexe2x80x9d resulting from the practice thereof can consist of selection(s) from the group consisting of:
calcium-valerate;
calcium-acetate;
calcium-propionate;
calcium-butyrate;
calcium-magnesium-acetate;
calcium-magnesium-propionate; and
calcium-magnesium-butyrate.
Further, in any of the foregoing examples, the separation of cellulase can also be performed, with a preferred approach thereto being by a size exclusion chromatography procedure.
It is also noted that any of said methods can provide a solution remaining after practice of the last step therein which has a reduced BOD as compared to the original waste stream or anaerobic digester system effluent as provided in step a.
It is further noted that the volatile fatty acid salt xe2x80x9cpaunchatexe2x80x9d produced by any of the above methods is suitable for use as deicer.
The invention will be better understood by reference to the Detailed Description Section of this Specification, in conjunction with the Drawings.
It is therefore a primary purpose and/or objective of the present invention to provide economical, easy to practice, methodology for separating-out volatile fatty acids, enzyme and possibly other protein components from waste streams and anaerobic digester effluents, and providing said separated-out components in forms which have economical value.
It is another purpose and/or objective of the present invention to provide systems for practicing the methodology.
Other purposes and/or objectives of the present invention will become clear from a reading of the Specification.